Well, that's just kinda silly. Personally, I think anyone who calls themselves a "gamer" (regardless of gender) is socially retarded. Playing video games does not make anyone special or different an any way.
Also, anyone should be able to wear whatever shirt they want so long as they understand the reference be it a game, movie, band etc.

I think its not so much "female gamer", as "female gamer that is actually feminine and girlish". I have been a gamer my whole life but only recently have I ever bothered to really be feminine or care for myself really, so I went from just being a gamer to really being a girl, maybe thats the distinction?

The only problem with dating a gamer, of any gender, is the lack of hygiene. "I could play this game longer or I could take a shower and end up standing under and playing with the water for ten minutes before I clean myself". The way to get around that is to shower together; you still have fun and she gets a deep cleaning.